The presence of hydrogen cyanaide (HCN) in various gaseous streams complicates removal of additional impurities, e.g., removal of H.sub.2 S or CO.sub.2, and poses problems insofar as product quality and pollution control requirements are concerned. In particular, gas streams derived from the gasification of coal generally have significant minor quantities of HCN which must be dealt with before the gas is utilized.
Accordingly, a practical and efficient procedure for removing impurity HCN might have gret economic importance. The invention is such a process.
In my copending application entitled Removal of HCN from Gaseous Streams, U.S. Ser. No. 556,255, filed even data herewith, there is described a process in which an HCN-containing gaseous stream is contacted with an ammonium polysulfide solution to form ammonium thiocyanate, and at least a portion of the ammonium thiocyanate-containing ammonium polysulfide solution is removed and subjected to hydrolysis conditions to produce H.sub.2 S, NH.sub.3, and CO.sub.2. If the contact zone is operated with a substantial excess of polysulfide sulfur, significant quantities of molten sulfur will be produced in the hydrolysis zone. In some instances, it may be preferred not to operate in such fashion, i.e., with a large second liquid phase in the hydrolysis zone. The invention provides a method of removing HCN from gaseous streams which eliminates the need for so doing.